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Carbon dynamics: perspectives from ecosystem models. Sarah C. Davis Interface Meeting, Captiva Island Fl March 2, 2011. Major challenges. Long-term responses to climate change Effects of land use change. Outline. Approach to modeling Carbon trends in perennial grass crops
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Carbon dynamics: perspectives from ecosystem models Sarah C. Davis Interface Meeting, Captiva Island Fl March 2, 2011
Major challenges • Long-term responses to climate change • Effects of land use change
Outline • Approach to modeling • Carbon trends in perennial grass crops – belowground carbon sequestration • Land use issues and challenges • Carbon dynamics in forested ecosystems • aboveground carbon sequestration • Resolving long term responses of forests to climate change
Ecosystem modeling approach • Comparative ecosystem physiology • Comparative ecosystem biogeochemistry • Coupled to hypothesis-driven research
Net photosynthesis Leaf nitrogen content Example of a physiology-driven model (PnET) Realized gross photosynthesis Maximum gross photosynthesis GPP VPD PAR daylength Radiation Day temperature Night temperature Basal respiration Realized respiration NPP
Example of biogeochemistry- driven model Miscanthus x giganteus Parton et al. 1998
Above- vs. Below-ground Carbon Sinks • “Judicious management” can increase soil C • Lugo et al., 1986, Cerri et al. 1991, Izaurralde et al. 2000, Conant et al. 2001, Zan et al. 2001, Lal 2004 • Long-term carbon sequestration more dependent on increasing aboveground biomass • Schlesinger 1990, Richter et al. 1999, Schlesinger and Lichter 2001
EcosystemModels Tools for characterizing effects of both climate change and land use change Ecosystem productivity Atmospheric CO2 Biomass Harvest Ecosystem productivity Atmospheric CO2
Miscanthus and Switchgrass Davis , Parton et al. 2011 in press
Net Greenhouse Gas Fluxes Corn Miscanthus Switchgrass no fertilizer Switchgrass fertilizer Davis , Parton et al. 2011 in press
Soil Carbon Corn Miscanthus Switchgrass no fertilizer Switchgrass fertilizer Davis , Parton et al. 2011 in press
Land Use Change • A controversial issue for biofuels • Scaling beyond the case study is very difficult • Political forces are sometimes inhibitory • We need internationally standardized land use monitoring and databases • See Davis et al. 2011 in Journal of the Royal Society Interface
Eastern US Forest Carbon Sink • Regenerating forests • Caspersen et al. 2000, Schimel et al. 2000, McGuire et al. 2001, Hurtt et al. 2002, Goodale et al. 2002, Houghton 2003, Nabuurs et al. 2003 • Climate change • Schimel 1995, Cao & Woodward 1998, Kicklighter et al. 1999, Joos et al. 2001, Joos et al. 2002, McGuire et al. 2001
Loblolly pine production over time Drake, Davis, Raetz, DeLucia 2010 Global Change Biology
Photosynthetic Response to CO2 Ca = 12CO2 + 13CO2 Ci Ci :Ca is proportional to photosynthesis (A) Lower Ci:Ca means more 13C is assimilated
Do young and old forests respond similarly to climate change?
Old forests have experienced the changing atmospheric CO2 concentration Is the gradual response to CO2 over a century similar to the instantaneous response?
Summary • Soil carbon sequestration is greater in perennial crops than row crops. • There is a need for internationally standardized land use data. • Older forests may be more responsive to increases in atmospheric CO2than younger forests.
Acknowledgements • Steve Del Grosso • Evan DeLucia • John Drake • Cindy Keough • Ernest Marx • Tim Mies • Steve Long • Bill Parton • Lisa Raetz
